Two Position, Two Velocity Synthesis of a Spherical Mechanism With Translating Center

In this paper we present a methodology for determining the link dimensions of a two-actuator device capable of guiding a part through two specified spatial positions. In addition, the device must be capable of producing two specified linear velocities, one at each spatial position. This represents a spatial pick-and-place operation with a fixture holding the part at both ends. The device we seek to dimension is a spherical four-bar mechanism mounted on a prismatic joint. In order to achieve the specified positions and velocities, we assume the following actuation scheme. The spherical four-bar is actuated to start the motion from the first position, then moves in tandem with the prismatic joint. The prismatic joint completes its slide, and then the spherical four-bar aligns the body with the second position. An example of the methodology is shown.